固溶-大变形-时效下7085铝合金的强化机理

以固溶—时效和固溶—大变形(压缩、ECAP)—时效加工的7085铝合金为实验对象,分别采用拉伸试验机、X射线衍射仪(XRD)和晶体微区取向分析技术(EBSD)对7085铝合金的拉伸性能、内部的位错密度、单元边界(小角度晶界)和晶粒边界(大角度晶界)进行研究,结合拉伸试验测得的屈服强度,定量计算强化项对不同状态下铝合金的强化贡献。结果表明,相比常规固溶—时效工艺,固溶—大变形—时效工艺加工的7085铝合金的拉伸强度从381.2MPa分别提升到475.6和543.3 MPa;位错强化显著提高,从零分别提高到107.4和180.6 MPa;小角度强化显著提高,从10.4 MPa分别提高到89.1和116.4 MPa。7085铝合金强度提高来源于材料内部的位错和小角度晶界;固溶后的大变形加速了时效,降低了时效沉淀强化。并且发现强烈塑性变形加工(ECAP)的强化效果高于传统塑性变形加工(压缩变形)的效果。

The research of Strengthening mechanisms of 7085 aluminum alloy by solution-large-deformation

Experimental object of this paper is the solution-aging and solution-large deformation (compression,ECAP)-aging of 7085 aluminum alloy. Through the tensile testing machine and scanning electron microscope (SEM) to test the tensile properties and fracture analysis. Internal dislocation density, low angle grain boundary and high angle grain boundary of 7085 aluminum alloy under different states were characterized through X-ray diffractometer (XRD) and Electron Back Scattering Diffraction (EBSD) .Combined tensile test measured yield strength, strengthen the contribution of the large deformation strengthening aluminum items of the quantitative calculation.The results show that, compared with conventional solution-aging treatment, the solution-large deformation - aging treatment can significantly refine grain size, increase the number of low angle grain boundary, prompt uniform distribution of precipitated phase so as to advance yield stress. Especially, Equal Channel Angular Pressing (ECAP) is more effective than compression in improving overall performance. Large deformation processing of 7085 aluminum alloy also makes a lot of internal accumulation of dislocations, large deformation processing was improving performance mainly depends on the alloy dislocation strengthening and small-angle grain boundary strengthening, alloy internal solid solution strengthening and second phase strengthening has been weakened by large deformation processed.